1. Field of the Invention
The present invention relates to a communication control method for a communication control equipment connected to a network. More particularly, the present invention relates to a mobil communication control equipment, an information management equipment and a communication service control method. Among others, the present invention relates to a mobile communication control equipment in a mobile communication system adopting a Mobile IP protocol and an information management equipment in a communication system adopting an SIP protocol.
2. Description of the Related Art
Studies on the IP (Internet Protocol) for a mobile communication network are becoming vigorous nowadays. The IETF (Internet Engineering Task Force) is trying to standardize the specifications of Mobile IPv6 (e.g., refer to Mobility Support in IPv6<draft-ietf-mobileip-ipv6-24.txt>, Work in Progress §4.1). The constituent elements of a Mobile IPv6 network include a mobile node (MN), a home agent (HA) and a correspondent node (CN). MN is given an unique IP address (home address) which will not change even after movement of MN. A link having the same prefix as that of the home address is called home link. The prefix is a network portion of the IP address. As MN moves to a link other than the home link (a link at the movement destination is called visited link), MN acquires an IP address in the visited link. This address is called Care of Address (hereinafter represented by CoA). Application of MN performs communications by using the home address. The application of MN can perform communications without using CoA.
When MN moves to a visited link, it receives router advertisements periodically transmitted from a router existing in the visited link. MN knows the movement from the home link to the visited link, by detecting the prefix which is different from that of the home address and is contained in the router advertisement. A router advertisement message is defined in Neighbor Discovery for IPv6 (refer to IETF RFC2461, Neighbor Discovery for IP Version 6 (IPv6) §3). This message is used to notify another node in the same link of the presence of the router. When MN knows the movement to the visited link, it registers its location in HA. HA stores, in a Binding Cache, correspondence information (binding information) between a Care of Address and the home address of MN existing in a link other than the home link. In order to capture a packet transmitted from CN to the home address of MN, HA multicasts a Gratuitous Neighbor Advertisement to operate as a proxy of MN.
In the following, description will be made on a process of transmitting a packet from CN to MN.
CN transmits a packet to the home address of MN. HA captures the packet destined to the home address of MN. HA searches data in the Binding Cache to acquire CoA corresponding to the home address of MN. HA adds (encapsulates) an IP header for CoA destination to the received packet and transmits it. A capsulation section between HA-MN is called mobile tunnel. When MN receives the packet destined to CoA, it removes (decapsulates) the previously added IP header to recover the original packet. MN may perform route optimization by notifying CN of the binding information of MN itself.
SIP (Session Initiation Protocol) has been paid attention as a session control protocol for an IP network (refer to IETF RFC3261, SIP: Session Initiation Protocol §4). SIP is the protocol for session control of IP multimedia communications standardized by the IETF. Typical Service utilizing SIP is VoIP (Voice over IP). VoIP pertains to technologies of sending/receiving voice information over an IP network. For VoIP communications by SIP, a virtual communication path (session) is set between communication apparatuses prior to starting communications. IP-packetized voice data is transferred on the set communication path. In VoIP communications, SIP creates, maintains and terminates sessions between communication apparatuses.
The IETF is under studies on the concept “presence” (e.g., refer to IETF RFC2778, A model for Presence and Instant Messaging §2.1). The presence indicates presence information and a state of a terminal. Service of notifying the presence of a communication partner is called presence service. SIP is provided with a function of requesting and notifying an event (hereinafter called event notification function). The IETF is under studies on a transmission/reception method for presence information utilizing the event notification function of SIP (e.g., refer to IETF RFC3625, Session Initiation Protocol (SIP)-Specific Event Notification §1.1).
In a conventional presence service providing system, a terminal providing presence information supplies a presence server with location information (e.g., an IP address) and the like, and another terminal referring to presence information refers to the presence information stored in the presence server, using the event notification function. The presence server received the event notification function may authenticate the terminal by referring to the presence information. In accordance with the authentication result, the presence server controls open/not-open of the presence information.
In a conventional Mobile IP communication system, application of a mobile terminal uses a home address for communications, and does not use a Care of Address. Therefore, the application of the mobile terminal does not notify a Care of Address to a communication apparatus such as a presence server. A presence service providing method for a Mobile IP compatible mobile terminal is as follows, which is conceivable when a conventional communication control method is used.
First, a mobile terminal registers its Mobile IP location in HA. Next, the mobile terminal notifies a presence server of the presence information of the terminal. Although the presence information contains in some cases an IP address, this notified IP address is the home address. Next, an information delivery server acquires the presence information of the mobile terminal from the presence server. This presence information contains in some cases the home address of the mobile terminal. Therefore, when the information delivery server provides service by using the IP address of the mobile terminal, it is necessary to use the home address as the IP address, posing the problem that service cannot be provided to a Care of Address of the mobile terminal.
The service to a Care of Address may be information delivery service, originating call restriction service, terminating call restriction service in a network visited by a mobile terminal. If Mobile IP route optimization is performed, MN notifies arbitrary communication partners of binding information, posing the problem that security cannot be maintained.